Unable to open Name and Address Book (names.nsf) due to error <error>. Locations cannot be used until the problem has been corrected.

What happened

You're using mobile Notes, and you chose File - Mobile - Call Server, or some other command that causes Notes to check your Personal Address Book for remote connection documents. Notes either found no Personal Address Book database or didn't recognize the one you have installed.

What you can do

If you don't have a backup of NAMES.NSF, you can create a new Personal Address Book with File - Database - New, using the Personal Address Book template (PERNAMES.NTF). Ask your Domino administrator for assistance if necessary.